//递归求解累加和

#include <stdio.h>

int s( int n , int m )
{
	int sum;
	if ( n==m )
	{
		sum = n;
	}
	else if ( n<=m )
	{
		sum = s( n , m-1 );
		sum = sum + m;
	}
	return sum;
}	

int main()
{
	int n,m,result;
	scanf("%d %d",&n,&m);
	result = s( n , m );
	printf ("The sum from %d to %d is %d.\n",n,m,result);
	return 0;
}
